1. Field of the Invention
The present invention relates to an image storage apparatus for storing and reproducing digital images.
2. Description of the Related Art
A digital fluorograph device (hereinafter called "DF device") is an X ray diagnosis apparatus to which the digital technology of converting analog video signals from a TV camera into digital signals is applied. There is a digital image storage apparatus which stores and reproduces digital images generated by such a DF device.
FIG. 1 shows the structure of a conventional image storage apparatus which uses a digital video tape as a recording medium. It is assumed in this case that a plurality of DF system 1 and 2 and a plurality of work stations 3, 4 and 5 are located in a hospital. To allow those DF systems 1 and 2 and work stations 3, 4 and 5 to share fewer digital VCRs to shorten the long wait time or similar shortcomings, the DF systems 1 and 2 and the work stations 3-5 share only a cassette library unit 11 and individually have digital VCRs (VTRs) 6 to 10 one each. Cassette exchange by a video cassette changer in the cassette library unit 11 is responsive to the DF systems 1 and 2 and the work stations 3 to 5 under the control of a control unit 12.
This conventional image storage apparatus has the following problems.
First, the conventional apparatus requires digital VCRs equal in number to the total number of work stations and DF systems.
Secondly, two types of images recorded on the same cassette tape cannot be monitored by separate work stations.
Thirdly, since image reproduction is executed using a digital VCR, magnetic heads wear out heavily.
Fourthly, images generated by a DF systems cannot be recorded and reproduced at the same time.
Fifthly, a data error caused by a defect on a video tape, tracking error, crosstalk, etc. cannot be corrected.
The following is the sixth shortcoming. While a 512.times.512 matrix of data can be written on a single track of a video tape by the NTSC system, images for medical purposes are generally formed in a high definition of a 1024.times.1024 matrix so that images of a 1024.times.1024 matrix are divided into four fields to be respectively written on consecutive four tracks. At the time of reproduction, as the tape runs, field data should sequentially be rearranged into one frame to construct one image. This results in various restrictions: the frame rate becomes lower, fast forward playback is not possible and reverse playback is not possible.